This invention concerns a method to manage an insulated cooling bed, and also the relative insulated cooling bed used in the method.
The invention is applied in production plants for in-line rolling starting from continuous casting, whether the plants are completely hot-loaded, when the production of the casting plant is higher than or equal to the production of the rolling mill, or the plants are mixed-loaded, when the production of the rolling mill is higher than that of the casting plant and therefore there is a mixed feeding system of hot/cold-load.
The state of the art includes in-line rolling plants where the slab leaving the continuous casting machine is sheared to size in sections of the desired length, which are loaded in a cooling bed by means of the appropriate transfer and subsequently sent to the rolling train through a reheating furnace in order to restore and equalise the temperature of the slab.
In such rolling lines, the cooling bed placed downstream of the continuous casting machine and the shearing unit is basically used as a functional connection between the functioning sequences of the casting plant and those of the rolling mill. In other words, the cooling bed functions as a variable accumulator for the billets as they are produced by the continuous casting, and also as a positioning seating for the cold billets in the case of mixed loading, the billets then being fed to the reheating furnace and then to the rolling mill.
The cooling bed also functions as an emergency store in the event that any accidents, blockages, maintenance operations on or substitution of the rollers, changes of channel or other, should block or slow down the rolling train while the casting machine continues to function.
Cooling beds known to the state of the art, since they work at ambient temperature, have the problem that they cause a considerable fall in temperature in the billets which have gradually accumulated.
This is also due to the fact that these billets remain in the cooling bed for quite a long time because of the sizes, often considerable, of the beds themselves; however these sizes are necessary if the beds are to function as variable accumulators, as the rolling plant requires.
Therefore, the reheating furnace situated downstream of the cooling bed has to perform a burdensome task of restoring the temperature of the slab, which involves a considerable consumption of energy.
Moreover, this makes it necessary to reduce the feeding speed of the slabs to the rolling train, in order to restore the slabs to an optimum temperature or, alternatively, makes it difficult to obtain the most suitable temperatures to achieve an efficient rolling.
Furthermore, with cooling beds known to the state of the art it is not possible to achieve efficient feeding systems of the slabs to the furnace either with a completely hot load or with a mixed load, given the structural and functional problems caused by loading the billets from the casting plant to the bed, and unloading the billets from the bed to the rollerway to feed the billets to the furnace.
JP-A-59-039414 includes a cooling bed with an upper movable cover.
The upper movable cover serves to cooperate with one lengthwise part of the cooling bed or the other.
The upper movable cover is equipped with autonomous ventilators which feed specific ventilation mouths which cooperate with temperature monitors to control the cooling gradient.
In this way it is possible to control the cooling of the billets placed under the movable cover and to obtain the desired heat treatment.
DE-A-3541654 includes normal reheating furnaces with thrust operated lateral translation, associated with manipulator devices for the slabs when a complete and precise uniformity of temperature is required throughout the slab.
Neither of these two prior art documents deals with the problem posed by this invention, nor do they provide any valid indication which might lead to the problem posed by this invention, or to the solution thereof.
It should be remembered that modern technology requires that the billet produced by continuous casting must go directly, and in the hottest conditions possible, to the rolling mill, in order to save on time and energy, the billet transiting directly through the reheating and temperature-equalisation furnace.
Unfortunately, the perfect synchrony between casting and rolling mill does not exist, both because of repetitive factors (change of casting, change of crystalliser, routine maintenance, etc.) and also because of jamming or incidents (slowdowns, breakages, non-routine maintenance, etc.).